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This uses the actual size of the native views dropdown to decide
if it will be drawn upwards or downwards, to the left or to the
right.

Screenshots can be found at: https://drive.google.com/open?id=1F43ccvwErhPS7hEmdKWl90i0yHmd3-7J

Bug: 768881
Change-Id: Iedc166b7c7edbdfe324c7657f7f319dc4032487f
Reviewed-on: https://chromium-review.googlesource.com/1036286
Commit-Queue: Fabio Tirelo <ftirelo@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Tommy Martino <tmartino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557864}